The present invention generally relates to antennas, and more particularly, to an ultra-broadband antenna.
Most man-carried antennas have two disadvantages. First, they have a distinctive visual signature that uniquely identifies a radio operator and accompanying officer nearby, making them vulnerable to sniper fire. Because disruption of command, communications, and control is a paramount goal of snipers, reduction of the visual signature of the antenna is highly desirable. The second disadvantage is that man-carried antennas are generally specialized to one radio and often a very narrow band.
Therefore, a need exists for a broadband, man-carried antenna that does not have a readily identifiable visual signature.
The present invention provides an antenna that includes a liner shaped to fit over a helmet; a first RF element attached to the liner; a second RF element attached to the liner so that the first and second RF elements are separated by a gap; an RF feed electrically connected to the first RF element for providing RF energy to the first RF element; a ground feed electrically connected to the second RF element; a first shorting strap that is electrically connected to the first and second RF elements opposite from the RF feed; and a second shorting strap electrically connected to the first and second RF elements between the first shorting strap and the RF feed. The shorting straps are used to match the impedance of the antenna to an external load. A impedance matching circuit which may include elements such as capacitors, inductors, and resistors, may be connected in series between the RF feed and the first RF element to further reduce any impedance mismatch between the antenna and external load. In another embodiment of the invention, the RF elements may be mounted directly to the helmet, in applications where the helmet is made of a dielectric material.
An important advantage of the invention is that the open crown (i.e., no RF element is present in this area) at the top of the helmet allows the antenna to operate with a voltage standing wave ratio (VSWR) in the range of 3:1 over a bandwidth of 440-2310 MHz.
Another advantage of the invention is that it may be configured to fit over a soldier""s helmet and exhibit practically no visual signature.
These and other advantages of the invention will become more apparent upon review of the accompanying drawings and specification, including the claims.